//根据二叉树创建字符串
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution3 {
    public String tree2str(TreeNode root) {
        StringBuilder stringBuilder = new StringBuilder();
        tree2strChild(root,stringBuilder);
        return stringBuilder.toString();
    }

    private void tree2strChild(TreeNode t,StringBuilder stringBuilder) {
        if(t == null) {
            return ;
        }
        stringBuilder.append(t.val);
        if(t.left != null) {
            stringBuilder.append("(");
            tree2strChild(t.left,stringBuilder);
            stringBuilder.append(")");
        }else {
            if(t.right == null) {
                return;
            }else {
                stringBuilder.append("()");
            }
        }
        //判断右树
        if(t.right != null) {
            stringBuilder.append("(");
            tree2strChild(t.right,stringBuilder);
            stringBuilder.append(")");
        }else {
            return;
        }
    }
}